An apparatus for eye examination and treatment requires that a patient's eye be fixed in position with respect to the eye examination or treatment instrument. There is thus a need to initially and preliminarily position the patient head to approximately align the eye, and then to engage some fine adjustment to accurately align the selected eye (or both eyes) with the eye examination or treatment instrument.
Due to the fact that the head size and the relative position of the eye(s) with respect to the chin are different for different patients, it is necessary to adjust the head support to accommodate the various physical characteristics of a patient's head. Some prior art solutions are based on a relative positional adjustment of the chinrest with respect to the forehead rest, which could be followed by a positional adjustment of chinrest/forehead-rest assembly with respect to the eye examination/treatment instrument, or a positional adjustment of the eye examination/treatment instrument with respect to the assembly. Generally speaking, these movements are realized using manual adjustments (with the help of, for example, a joystick), which typically are inaccurate, repetitive, and time-consuming. Meanwhile, these movements also require a locking mechanism, or locking mechanisms, which typically require manual input from the operator to fix the relative position of the patient's head with respect to the instrument, which incurs more expense (see for example U.S. Pat. Nos. 3,594,072; 4,128,317; 4,139,280; 4,431,279; 4,790,647; 5,000,563; 5,125,731; 5,220,361; 5,907,387; 6,481,848; European Pat. No. EP 0054273; U.K. Patent No. 268,771; and PCT Pat. No. WO 01/49223, each of which is hereby incorporated herein by reference).
In spite of the fact that motorized movement may be more expensive, it can provide much better movement and positioning accuracy. At the same time, the need for locking the movable part(s) in position can be eliminated. When the motor stops at the correct position, the motor drive can be designed such that the movable part is locked in position. Existing references disclose such motorized movement, restricted to one- or two-dimensional movement of the patient support only (see, for example, U.S. Pat. No. 5,491,757 and Japanese Pat. No. JP11225958, hereby incorporated herein by reference), or to the three-dimensional movement of the eye examination/treatment instrument with respect to the chinrest/forehead rest assembly (see for example, U.S. Pat. Nos. 3,475,075; 5,907,387; and 6,575,575, hereby incorporated herein by reference).
Motorized movement of the eye examination/treatment instrument is typically more costly than motorized movement of the chinrest or forehead rest, due to the fact that the eye examination/treatment instrument typically has a multitude of cables that need to be routed between the moving parts of the instrument. A motorized eye examination/treatment instrument is also significantly bulkier due to the internal space requirement to accommodate the relative movement of the components. Moreover, conventional motorized mechanical systems generally are not very compact.
A major issue associated with eye examination or treatment is that a patient generally cannot maintain his or her head pressed against the chinrest and forehead rest, and hence fixed in position for a long time, due to fatigue, anxiety, loss of concentration, and other reasons. In general, an operator has to repeatedly discern whether the patient head is in position, and has to repeatedly remind the patient to reposition his or her head. This practice can be bothersome for both the operator and the patient, such that a solution is desired. Previous solutions have proposed that a headband is used to force the patient to fix his or her head to rest against the chinrest/forehead-rest assembly. This is, of course, intimidating and uncomfortable for the patient and is hence generally not practiced. The most recent solution is the use of sensors to give off a signal when the patient's head is moved away from the chinrest or forehead-rest, thereby automatically and politely reminding the patient to move his or her head back in position (see, for example, U.S. Pat. Nos. 5,387,952; 5,591,175; and PCT Pat. No. WO 00/13571, hereby incorporated herein by reference). One problem associated with these sensor based solutions is that, even though the patient is reminded to reposition his or her head back in contact with the chinrest and the forehead-rest, there is still no guarantee that his or her eye is in exactly the same original position as required.